The Android ecosystem offers incredible variety—from Samsung's premium Galaxy S series to Google's AI-powered Pixels and OnePlus's value flagships. This variety means used Android phones can be amazing deals, but also present unique challenges: OLED burn-in, unlocked bootloaders, carrier bloatware, and wildly varying software support timelines.
This comprehensive 2026 guide covers every test you need to perform before buying a used Android phone. Whether you're looking at a Samsung Galaxy S24, Google Pixel 8, or any other Android device, these 45+ checkpoints will help you avoid lemons and negotiate fair prices.
2026 Update: This guide covers Samsung One UI 6+, Google Pixel with 7 years of updates, and the latest security features. Special attention to OLED burn-in testing and battery health verification methods.
Before Meeting the Seller
Android phones have more variation than iPhones, making pre-meeting research crucial. Verify the exact model, carrier compatibility, and software support before traveling to inspect.
Essential Pre-Meeting Requests
1. Request IMEI Number
Ask seller to dial *#06# and send screenshot. Then verify:
- • IMEI Check: Use imei.info or swappa.com/imei to verify it's not blacklisted
- • Carrier Status: Check if locked to specific carrier
- • Model Verification: IMEI reveals exact model variant (US, International, etc.)
2. Verify Model & Variant
Android phones have regional variants with different features:
- • Samsung: SM-S928U (US) vs SM-S928B (International) - different processors!
- • Pixel: Usually universal, but verify mmWave support for your carrier
- • OnePlus: NA variant vs Global variant (band differences)
3. Check Software Support Timeline
Android update support varies dramatically by manufacturer:
Best Support (2026):
- • Google Pixel 8+: 7 years
- • Samsung Galaxy S24+: 7 years
- • Samsung Galaxy S23: 4 years
Check Before Buying:
- • OnePlus: 3-4 years typically
- • Xiaomi: 3 years
- • Budget brands: 1-2 years
🚫 Walk Away If:
- • IMEI comes back as blacklisted/lost/stolen
- • Seller refuses to provide IMEI before meeting
- • Phone is carrier locked and seller won't unlock it
- • Software support has already ended (security risk)
- • Price is suspiciously low (likely stolen or problematic)
Physical Inspection
Android phones come in various build qualities. Premium flagships use glass and aluminum, while mid-range devices may use plastic. Inspect accordingly and look for signs of drops, water damage, or repairs.
Exterior Inspection Checklist
Display Glass
- • Check for cracks, chips at all angles
- • Look for scratches under bright light
- • Verify screen protector isn't hiding damage
- • Check curved edges (Samsung) for chips
Back Panel
- • Glass backs: check for cracks
- • Camera bump area for scratches
- • Verify color matches listing
- • Check for case marks/discoloration
Frame & Buttons
- • All corners for dents/dings
- • Power button responsiveness
- • Volume buttons feel and click
- • SIM tray for damage
Ports & Openings
- • USB-C port for debris/damage
- • Speaker grills for blockage
- • Microphone holes clear
- • Headphone jack (if present)
Water Damage Indicators
Android phones have Liquid Damage Indicators (LDI) in the SIM tray slot. Remove the SIM tray and shine a flashlight inside:
- • White/Silver dot: No water damage detected
- • Pink/Red dot: Water contact has occurred
- • Also check for corrosion around charging port
- • Fog under camera lenses indicates water intrusion
💡 IP Rating Reality Check
Even phones with IP68 ratings (Samsung S series, Pixel) can suffer water damage. The seals degrade over time, especially if the phone was dropped or repaired. Water resistance is never permanent.
Display & OLED Burn-In Testing
OLED screens on Android phones are susceptible to burn-in—permanent ghost images from static content. This is the most common issue with used Samsung and other OLED Android phones.
OLED Burn-In Test Procedure
Download a Burn-In Test App
Search Play Store for "Screen Test" or "Display Tester". These apps display solid colors for burn-in detection.
Test with Gray Screen
Display 50% gray at full brightness. This is the best color for revealing burn-in. Look for ghost images of navigation bars, keyboards, or app icons.
Check Common Burn-In Areas
Status bar area (top), navigation bar (bottom), keyboard area (lower half), and any app icons that were frequently on screen.
Test All Solid Colors
Cycle through red, green, blue, white, and black. Look for dead pixels (not lighting up) or stuck pixels (always one color).
Display Feature Tests
Touch Response
- ☐ Open drawing app, test entire screen
- ☐ Check all corners for dead spots
- ☐ Test multi-touch (pinch to zoom)
- ☐ Verify palm rejection works
High Refresh Rate
- ☐ Enable 120Hz in display settings
- ☐ Scroll through long lists smoothly
- ☐ No stuttering or frame drops
- ☐ Adaptive refresh working
🔴 Display Deal-Breakers
- • Visible burn-in on gray screen test (won't get better)
- • Dead pixels in clusters (indicates panel failure)
- • Green or pink tint on low brightness (Samsung issue)
- • Touch not responding in specific areas
- • Screen flickering at any brightness
Battery Health Testing
Unlike iPhones, Android doesn't have a universal built-in battery health indicator. However, Samsung and some other manufacturers now include this feature, and third-party apps can estimate battery condition.
Battery Health by Brand
Samsung Galaxy (One UI 6+)
Settings → Battery → Battery Information
- • Shows battery capacity percentage
- • 95%+ = Excellent
- • 85-94% = Good
- • Below 85% = Consider replacement
Google Pixel
Settings → Battery → Battery Usage → View Details (some models)
- • Not all Pixels show capacity
- • Use AccuBattery app for estimates
- • Check cycle count if available
OnePlus / Other Brands
Use third-party apps:
- • AccuBattery (most accurate over time)
- • CPU-Z (shows some battery stats)
- • Phone Info Samsung (Samsung specific)
Real-World Battery Test
If you can't verify battery health directly, run this practical test:
- Note the current battery percentage
- Use the phone normally for 15-20 minutes (web browsing, video)
- Battery should drain linearly, not in sudden drops
- Sudden 5%+ drops indicate degraded battery cells
- Phone shutting off above 10% = severely degraded battery
⚠️ Fast Charging Wear
Phones that were frequently fast-charged (especially Samsung 45W, OnePlus Warp) may have accelerated battery degradation. Ask the seller about their charging habits if possible.
Software & Security Status
Android's open nature means software status varies wildly. Check for Google account locks, unlocked bootloaders, custom ROMs, and rooted devices—all of which can indicate tampering or limit functionality.
Critical Security Checks
🔒 Factory Reset Protection (FRP)
Android's equivalent of Activation Lock. Essential check!
- Ask seller to remove their Google account (Settings → Accounts)
- Factory reset the phone in front of you
- Go through setup WITHOUT entering their credentials
- If it asks for previous owner's Google account = FRP locked. Walk away.
Samsung Knox/Find My Device
- • Samsung: Settings → Biometrics & Security → Find My Mobile (should be off)
- • All Android: Settings → Google → Find My Device (verify can be disabled)
- • Reactivation Lock must be disabled before purchase
MDM/Enterprise Enrollment
- • Check Settings → Accounts for work profiles
- • Look for "Device Admin" apps in Settings → Security
- • Enterprise-enrolled phones may be remotely lockable
- • If corporate managed, seller may not be legitimate owner
Bootloader & Root Status
Check Bootloader Status
An unlocked bootloader means the phone can run custom software:
- • Settings → About Phone → tap Build Number 7x
- • Developer Options → OEM Unlocking status
- • Samsung: Download Mode shows "OEM Lock: ON/OFF"
Why This Matters
- • Unlocked bootloader = possibly rooted/modded
- • Samsung Knox trips permanently if unlocked
- • Banking apps may not work on rooted phones
- • Warranty typically voided
Software Update Status
Check Settings → About Phone → Software Information:
- ☐ Android version is current for the device
- ☐ Security patch date is recent (within 3 months ideal)
- ☐ Check for pending updates and install to verify OTA works
- ☐ Verify phone isn't at end-of-life for updates
Camera System Testing
Android flagships now rival dedicated cameras. Test each lens, verify image stabilization, and check for dust or damage that affects image quality.
Camera Tests by Lens
Main Camera
- ☐ Tap to focus responds quickly
- ☐ Auto-exposure adjusts correctly
- ☐ OIS test: record video while walking
- ☐ No dust spots visible in photos
- ☐ Night mode activates and works
- ☐ Portrait mode blur is accurate
- ☐ 4K/8K video records smoothly
- ☐ No purple fringing on bright lights
Ultra-Wide Camera
- ☐ Switches smoothly from main camera
- ☐ Edge distortion acceptable for the model
- ☐ Color matches main camera
- ☐ No excessive noise in low light
Telephoto / Periscope
- ☐ Optical zoom engages (not just digital crop)
- ☐ Image stable at max zoom
- ☐ Focus works at various distances
- ☐ No mechanical clicking sounds
Front Camera
- ☐ Selfie quality acceptable
- ☐ Portrait mode/blur works
- ☐ Video call quality good
- ☐ Face unlock works (if applicable)
⚠️ Camera Lens Inspection
Shine a flashlight at each camera lens at an angle. Look for scratches, cracks, or internal dust/fog. Scratched lenses cause flare and haze in photos—this is not fixable without replacement.
Connectivity Testing
Verify all radios work correctly. Carrier compatibility is especially important for used Android phones due to regional variants and band support differences.
Cellular Network Tests
SIM Card Test
- • Insert your SIM card
- • Verify carrier name appears
- • Check signal strength
- • Make an outgoing call
- • Receive an incoming call
- • Send and receive SMS
5G/LTE Verification
- • Check network mode in settings
- • Verify 5G icon appears (if in 5G area)
- • Run speed test over cellular
- • Verify VoLTE/VoNR calls work
WiFi & Bluetooth Tests
WiFi Testing
- • Connect to 2.4GHz network
- • Connect to 5GHz network
- • Test WiFi 6E (if supported)
- • Run speed test
- • Walk to edge of WiFi range
Bluetooth Testing
- • Pair with earbuds/headphones
- • Test audio quality and stability
- • Verify Bluetooth LE works
- • Test range (30+ feet typical)
- • Try file transfer via Bluetooth
NFC & Other Connectivity
- ☐ NFC toggle works (Settings → Connected devices)
- ☐ Test Google Pay/Samsung Pay (add a card)
- ☐ GPS locks quickly (open Google Maps)
- ☐ GPS accuracy is precise (not jumping around)
- ☐ Android Auto/wireless connection works (if important to you)
Sensors & Hardware Testing
Android phones have numerous sensors that can fail independently. Use diagnostic codes or apps to verify all hardware is functioning correctly.
Built-in Diagnostic Codes
Samsung Diagnostics
Dial: *#0*#
- • Red/Green/Blue screen tests
- • Touch screen test
- • Speaker test
- • Sensor tests
- • Camera front/back test
Google Pixel Diagnostics
Settings → About Phone → Diagnostics
- • Run all tests option
- • Individual sensor tests
- • Battery diagnostics
- • Network tests
Sensor Verification Checklist
Biometric Sensors
- ☐ Fingerprint scanner (register YOUR fingerprint)
- ☐ Face unlock (if available, enroll YOUR face)
- ☐ Both work quickly and reliably (9/10+ success rate)
Motion Sensors
- ☐ Accelerometer (auto-rotate works)
- ☐ Gyroscope (compass app works, VR apps)
- ☐ Proximity sensor (screen dims during calls)
- ☐ Ambient light sensor (auto-brightness adjusts)
Audio Hardware
- ☐ All speakers work (play music)
- ☐ Earpiece clear during calls
- ☐ All microphones work (record voice memo)
- ☐ No distortion at high volume
- ☐ Haptic feedback/vibration motor works
💡 Quick Sensor Test App
Download "Sensor Test" or "Phone Doctor Plus" from the Play Store. These apps test all sensors and give pass/fail results for each component.
Master Testing Checklist
Use this interactive checklist when evaluating any used Android phone. Failed items should factor into your purchase decision.
Pre-Meeting Verification
Physical Condition
Display Quality
Battery Health
Software & Security (CRITICAL)
Camera System
Connectivity
Sensors & Hardware
2026 Used Android Pricing Guide
Use these reference prices to evaluate deals. Prices assume excellent condition, no burn-in, good battery, and unlocked.
Samsung Galaxy Series
| Model | 128GB | 256GB | 512GB+ | Updates Until |
|---|---|---|---|---|
| Galaxy S24 Ultra | - | $850-950 | $950-1100 | 2031 |
| Galaxy S24+ | - | $650-750 | $750-850 | 2031 |
| Galaxy S24 | $500-600 | $550-650 | - | 2031 |
| Galaxy S23 Ultra | - | $650-750 | $750-850 | 2027 |
| Galaxy S23 | $400-475 | $450-525 | - | 2027 |
| Galaxy Z Fold 5 | - | $900-1050 | $1000-1150 | 2027 |
| Galaxy Z Flip 5 | - | $500-600 | $550-650 | 2027 |
Google Pixel Series
| Model | 128GB | 256GB | 512GB+ | Updates Until |
|---|---|---|---|---|
| Pixel 9 Pro XL | $750-850 | $800-900 | $900-1000 | 2031 |
| Pixel 9 Pro | $650-750 | $700-800 | $800-900 | 2031 |
| Pixel 9 | $500-575 | $550-625 | - | 2031 |
| Pixel 8 Pro | $500-575 | $550-625 | $650-725 | 2030 |
| Pixel 8 | $375-450 | $425-500 | - | 2030 |
| Pixel 8a | $300-375 | $350-425 | - | 2031 |
💡 Best Value Recommendations
Best Overall Value:
Google Pixel 8 - 7 years updates, great camera, ~$400
Best Premium Value:
Samsung S23 Ultra - Best camera zoom, ~$700